Suffolk Downs will dramatically shrink the “sea of asphalt” around the East Boston racetrack and increase plantings and gardens, as a key selling point of its bid for casino development rights, track officials say.

The revamped development plans are the first major update to the Suffolk Downs casino design since the track initially rolled out plans for a $1 billion “urban oasis’’ last June. The new details come as Suffolk Downs, once the unchallenged front-runner for the state’s most lucrative casino license, is facing tough new competition from ­rival projects.

The new designs, produced by the architectural firm Sasaki Associates of Watertown, includes an overhaul of the main entrance to the property off Route 1A, which passes between a homely field of fuel tanks and the densely developed Orient Heights neighborhood. The new entrance calls for a winding boulevard through newly planted fields and a buffer of new forest, leading to a horseshoe-shaped hotel.

The $10 million to $15 million grounds plan would reduce pavement on the site by 30 percent, in part by cutting the number of surface parking spaces from the current 6,300 to 1,900. Suffolk Downs would add a new parking garage to hold 2,400 to 2,500 cars, and create another 450 parking spaces under the hotel development, said track officials.

“This is a really stunning vision for how the property can look in the future, compared to what it looks like now,” Chip Tuttle, chief operating officer of Suffolk Downs, said Tuesday. “It’s a part of our commitment to having the most sustainably designed gaming property in the United States.”

Protecting the environment, designing energy-efficient buildings, and using sustainable materials are also competitive factors that will help decide which casino developer receives the coveted license in the Greater Boston region.

Suffolk Downs, with partner Caesars Entertainment, is locked in a winner-take-all contest with Las Vegas developer Steve Wynn, who has proposed a gambling resort in Everett, and Foxwoods Resort Casino, which has joined a casino project in Milford, about 35 miles from Boston.

The state’s 2011 casino legislation calls for casino proposals to be judged against the Leadership in Energy and Environmental Design ratings, known as LEED, created by the US Green Building Council. The legislation calls for a rating of gold or higher.

“We’re aspiring to go above and beyond that in our ­approach,” said Tuttle. The track is also investigating solar panels, rooftop gardens, ways to harvest rainwater, and other green initiatives.

Casino projects will also be judged on job creation, financial strength, creativity in design, and other factors. The state gambling commission, which controls the state’s casino licenses, is still deciding how to weigh the criteria, but “clearly, sustainable construction and operation is going to be a significant factor,” said Stephen Crosby, the commission’s chairman.

For much of 2012, Suffolk Downs appeared to have an open path to the most lucrative casino license in the state, as the only viable applicant. Wynn tried to build support in Foxborough early last year for a casino next to Gillette Stadium, but the project hit intractable local opposition, and Wynn dropped the plans.

Developer David Nunes long maintained that he would compete for casino development rights on a site he controls in Milford, but the proposal showed little public progress in 2012. Caesars chief executive Gary Loveman doubted openly that Nunes would be an applicant.

Wynn made a surprising return to Massachusetts in late November. He gained control of vacant industrial land on the Mystic River for a planned $1 billion hotel and casino. The company has not yet shared the details of the project, but Wynn has a reputation in the casino industry for innovative designs.

Nunes kept his promise to file an application, beating the deadline by 10 minutes. His project took a huge leap forward in February when Foxwoods in Connecticut joined the effort as a stakeholder and the casino’s operator, if it wins a license. Foxwoods brought instant credibility and name recognition to the proposal, giving the gambling commission a distinct suburban alternative to the urban applicants.

By the numbers

30% - The reduction in pavement in the latest Suffolk Downs casino design.

70% - The reduction in surface parking spaces at the site. The track would build a parking garage to hold up to 2,500 cars and create another 450 spaces under the hotel development.